The building page contains what is currently constructed within your castle.
Right click menu
The right-click menu contains several actions that can be done on a building
Upgrade - Manually start the building upgrading, if the prerequisites have been made and no other construction is ongoing.
Demolish - Same as the in-game Free Demolish option.
Demolish Instantly - Uses gems to remove the building instantly.
Finish With Gems - Finishes the construction using gems.
Finish With Speed-Ups - Finishes the construction using Speed-Up items.
Cancel Build - Cancel the construction.
Set as Build Spam Target - Set this building as the target for the "Build Spam" Guild Bank Command.
Clear Build Spam Target - Removes this as the target for the "Build Spam" Guild Bank Command.
The location number to castle position are like so:
Changing Castle Skin
You can click the Dropdown next to the castle building to change your current castle skin.